Sheet-fed printing presses are widely used in lithographic printing. In these presses, printing blankets are utilized to pick up the inked image from the printing plate and then transfer this image onto the paper which is to be printed. These printing blankets are comprised of an outer layer, formed mainly of a polymeric material, and a backing material on one side of the outer layer. The other side of the outer layer is the printing surface which carries ink for printing. The blanket is wrapped on a cylinder to transfer an inked image from a printing plate to paper during the printing process.
To achieve high quality printing, the blanket must not slip or creep on the cylinder. The conventional method of securing the blanket to the cylinder has been to secure the leading and trailing edges of the printing blanket between a channel formed into a holding bar. This holding bar is then housed in a gap or groove extending axially along the surface of the cylinder.
A number of considerations must be kept in mind when mounting these blankets to the holding bar, the foremost of which is to make sure that the printing blanket will not separate from the holding bar when the blanket is stretched taut over the printing cylinder. Another factor is the simplicity of installation and time involved in attaching the printing blankets. Conventional methods utilize a mono or bicomponent glue such as epoxy or polyurethane resin which is viscous and difficult to apply evenly. Furthermore, there is about a 24 hour delay between the application of the glue and bar to the blanket for curing prior to actual use.
Accordingly, there is a need for fastening a holding bar to a printing blanket in an expedient and inexpensive manner so that it will be able to bear the necessary mechanical stresses due to tensioning the blanket on the cylinder.